Key logger are the software that monitors keystrokes activities performed by the victim. It records every keyword that was typed by the user includingE- mails, Password, Usernames, Bank accounts information..
etc. It sends log to the attacker E mail id. This can give your secret
information to the attacker email. By this attacker has access to your
accounts and email Ids.

Facebook HackingBy key logger you can hack alsoFacebook accountsof the people. You send key logger through Some files by attaching your key logger to that files. Once victim downloaded your files and execute his downloaded filesKey
logger also get activated with that files and start working. It start's
recording every keystroke which was typed by the victim and you get log
of the every keystroke to your E mail account. You get the username
and password of the victim Facebook account. It is so easy.

ProtectionAnti-virus
companies added information about known key logger in their anti virus
database. For new key logger one should update his antivirus everyday.
Keep updating your antivirus every day. This may help you detect key
logger and provide protection against key logger.

Install the firewall and this also help you to detect key logger and also prevent it.

Use
virtual keyboard while entering Usernames & passwords or any
important information about accounts (banks). As this technique prevent
the key logger by sending the important information to the attacker.Steps to open virtual Keyboard

Start > Programs > Accessories > Accessibility > On-Screen Keyboard

Some mostly used keylogger

RefogRevealer KeyloggerSuper Free KeyloggerActual Keylogger

Only for education purpose... Try at your own riski hope this post is helpful to you..... :D